$(function(){
 let $btn = $('input'),
     num = window.localStorage.getItem('num') || 0;

 $btn.val(`被按了 ${num} 次`);

 $btn.click(()=>{
   
   window.localStorage.setItem('num',++num);
   
   $btn.val(`被按了 ${num} 次`);


 });
});
